'reproof' originates from Latin, specifically the word 'reprobare', where 're-' meant 'again/against' and 'probare' meant 'to test, to approve'.

'reproof' changed from Latin 'reprobare' through Old French (reprover/reprouver) into Middle English forms such as 'repreve'/'reprofe' and eventually became the modern English noun 'reproof'.

Initially it carried the sense of 'to reject or disapprove' (from the Latin verb), and over time the noun came to mean 'an expression of blame or criticism' in modern English.